Quasi-separatrix layers [1]} are thin layers characterized by a finite, but sharp, gradient in the connectivity of the magnetic field, and are defined as regions where the squashing degree \(Q\)  is large ([2]}). QSLs are also locations where current layers easily develop, where (slip-running) magnetic reconnection can occur ([3]}; [4]}; [5]}), and they often coincide with the position of the flare ribbons ([6]}; [7]}; [8]}; [9]}).
